The present invention relates generally to a process for producing a propeller and, more particularly, to such a process for producing a steel propeller adapted to be mounted on the propeller shaft of a marine engine for use on a boat.
Metal propellers currently being used for such purposes are generally fabricated using a one-piece casting or precision casting process, i.e., by introducing a suitable metal alloy, such as, for example, bronze and steel, into a casting mold and then casting the propeller. Other processes may be used for fabricating small propellers for boats in which the blades are made separately from the hub or boss. In such propellers, the blades have tangential projections at the end of the coupling to the boss and the boss has grooves made to receive the tangential projections. In such a construction, the boss and blades form a single piece when the tangential projections on the blades are made to slide into the grooves.
In still another process for manufacturing small two-bladed steel boat propellers, a parallelepiped steel ingot is forged or otherwise molded to form a propeller.
The aforementioned processes each possess certain inherent disadvantages, all of which are overcome by the present process. Propellers which are manufactured by such casting processes usually have relatively thick profiles which cause them to be very inefficient in actual operation. such cast propellers inherently have thick profiles. Due to the mechanical resistance of the materials used in casting such propellers, it is generally impossible to reduce the thickness and therefore their profiles beyond a certain point. A disadvantage of the second mentioned process, i.e., where the blades are made independently of the boss, constructional requirements limit the cross section of the coupling between the blades and the boss resulting in a rather weak propeller.